Cell culturing techniques and cell culturing devices are well known in the art.
U.S. Pat. No. 5,888,807, issued to Palsson, et al, on Mar. 30, 1999, describes bioreactors in which diverse cell types are simultaneously cultured in the presence of appropriate levels of nutrients and growth factors. Such levels are achieved by substantially continuously perfusing the cells in the bioreactor while removing undesirable metabolic products.
U.S. Pat. No. 5,712,154, issued to Mullon, et al., on Jan. 27, 1998, describes a cell culture system comprising liquid nutrient and gas perfusion fibers that provide the appropriate culture conditions for cells located interstitially between the liquid nutrient and gas fibers.
U.S. Pat. No. 5,320,963, issued Knaack, et al., on Jun. 14, 1994, describes a bioreactor for perfusion culture of cells in suspension. The bioreactor of Knaack et al. has an inversely-conical tank which includes a cell culture zone and a cell settling zone disposed annularly relative to the cell culture zone in the upper region of the tank.